How do you change how much spaceship parts cost?

I want to change how much spaceship parts cost, so I went to the projects file to see how the game stores the information, and the parts are there, but on their lines for cost, it is set to -1. Where does the game actually store the information on how much they cost?

They're units.

Spaceship parts are also units. Their basic definition as units, including <Cost>, is in the CIV5Units.xml in the Units folder. But they're an oddball half-in and half-out sort of a "unit".

Oh, they're units. Thanks guys.